Antenna device

Abstract

An antenna device according to an aspect of the present disclosure includes a zeroth-order resonant antenna and a first-order resonant antenna. The zeroth-order resonant antenna includes a base plate, a platy radiation element, and a connection conductor connecting the base plate and the platy radiation element. The zeroth-order resonant antenna is configured to transmit and/or receive a first linearly polarized radio wave in all directions perpendicular to the first linearly polarized radio wave by zeroth order resonance. The first-order resonant antenna includes the base plate shared with the zeroth-order resonant antenna, and a first radiation element located on the same plane as the base plate. The first-order resonant antenna is configured to transmit and/or receive a second linearly polarized radio wave perpendicular to the first linearly polarized radio wave by first order resonance.

What is claimed is: 
     
       1. An antenna device comprising:
 a zeroth-order resonant antenna configured to transmit and/or receive a first linearly polarized radio wave in all directions perpendicular to the first linearly polarized radio wave by zeroth order resonance; and 
 a first-order resonant antenna configured to transmit and/or receive a second linearly polarized radio wave perpendicular to the first linearly polarized radio wave by first order resonance, wherein 
 the zeroth-order resonant antenna includes
 a base plate, 
 a platy radiation element spaced from the base plate, the platy radiation element facing the base plate, the platy radiation element being configured to be supplied with power, and 
 a connection conductor electrically connecting the platy radiation element and the base plate, 
 
 the first-order resonant antenna includes
 the base plate shared with the zeroth-order resonant antenna, and 
 a first radiation element located on a same plane as the base plate, the first radiation element being configured to be supplied with power, 
 
 the first radiation element has a first end connected to the base plate, and a second end configured to be supplied with power, 
 the first radiation element and the base plate of the first-order resonant antenna form a first closed loop, 
 the first order resonant antenna includes a second radiation element located inside the first closed loop, 
 the second radiation element has a first end connected to the base plate, and a second end configured to be supplied with power, and 
 the second radiation element and the base plate of the first-order resonant antenna form a second closed loop. 
 
     
     
       2. The antenna device according to  claim 1 , wherein
 a part or whole of the first radiation element does not overlap the platy radiation element in a direction perpendicular to the base plate. 
 
     
     
       3. The antenna device according to  claim 1 , wherein
 the platy radiation element has a polygonal shape having at least one acute internal angle and at least one obtuse angle, 
 a part of the platy radiation element located in a vicinity of a vertex corresponding to the at least one obtuse angle is configured to be supplied with power. 
 
     
     
       4. The antenna device according to  claim 1 , wherein
 the first-order resonant antenna is a first first-order resonant antenna, 
 the antenna device further comprises: 
 a second first-order resonant antenna different from the first first-order resonant antenna, wherein 
 the second first-order resonant antenna is configured to transmit and/or receive a third linearly polarized radio wave perpendicular to the first linearly polarized radio wave by first order resonance, 
 the second first-order resonant antenna includes
 the base plate shared with the zeroth-order resonant antenna, and 
 a third radiation element located on the same plane as the base plate, the third radiation element being configured to be supplied with power. 
 
 
     
     
       5. The antenna device according to  claim 1 , wherein
 the first-order resonant antenna is a first first-order resonant antenna, 
 the antenna device further comprises: 
 a third first-order resonant antenna different from the first first-order resonant antenna, wherein 
 the third first-order resonant antenna includes the base plate shared with the zeroth-order resonant antenna, and 
 the third first-order resonant antenna is configured to transmit and/or receive the first linearly polarized radio wave by first order resonance. 
 
     
     
       6. The antenna device according to  claim 1 , further comprising:
 a hollow casing that has a side face portion including a platy conductor, wherein 
 the base plate is located outside the casing and on the side face portion, and 
 the base plate is connected to the platy conductor of the side face portion. 
 
     
     
       7. The antenna device according to  claim 1 , wherein
 the antenna device is mounted on a vehicle, 
 the first linearly polarized radio wave is a vertically polarized wave, and 
 the second linearly polarized radio wave is a horizontally polarized wave. 
 
     
     
       8. The antenna device according to  claim 1 , wherein
 the antenna device is mounted on a vehicle such that the first radiation element is located on a front side of the vehicle with respect to the base plate.